Wireless communication node adapted to radiate antenna beams of different types

ABSTRACT

A wireless communication node comprising an antenna arrangement that is adapted to radiate at least one radiation beam of a first type and at least one radiation beam of a second type. Said at least one radiation beam of the first type has a first type beamwidth (BT1) and said at least one radiation beam of the second type has a second type beamwidth (BT2) that exceeds the first type beamwidth (BT1). Said at least one radiation beam of the first type is arranged for communication with at least a first other node, and where said at least one radiation beam of the second type is arranged for detection of changes in propagation paths for said other node and/or appearances of further other nodes.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/521,693, which has a section 371(c) date of Apr. 25, 2017, and whichis the U.S. National Stage of International Patent Application No.PCT/EP2016/056634, filed Mar. 24, 2016. The above identifiedapplications are incorporated by this reference.

TECHNICAL FIELD

The present disclosure relates to a wireless communication nodecomprising an antenna arrangement that is adapted to radiate at leastone radiation beam of a first type and at least one radiation beam of asecond type.

BACKGROUND

Massive beamforming is regarded as an important technical component for5G wireless communications. With massive beamforming, hundreds ofantenna elements are arranged to be used at the base station (BS) asopposed to only a few antennas in previous systems.

Many beamforming concepts rely on the base station (BS) using agrid-of-beams (GoB) approach. One such approach is that the BS transmitsreference signals in a number of beams, herein referred to as beamreference signals (BRS:s), in order to enable a user terminal, userequipment (UE), to measure which beam that is the best/most suitable.Such measurements could be based on, e.g., reference signal receivedpower (RSRP). The UE then reports an index for the best beam, or indicesto a number of the best beams to the BS. The RSRP for the correspondingbeams could also be reported to the BS. Based on these reports, the BScan decide which beam or beams to use for the data transmission.

The GoB typically consists of a number of predetermined fixed beams withbeamforming weights obtained from a, possibly oversampled, DFT (DiscreteFourier Transform) matrix. In order not to lose any information in thedata collected by the antenna elements, the number of beams in the GoBshould be at least as many as the number of antenna elements. This meansthat the number of beams in the GoB of a potential massive beamformingsystem at least could be several hundreds.

With many beams in the GoB, a high number of BRS:s may be required.

This could lead to pilot contamination, high consumption of radioresource elements for the pilots, and comprehensive measurementprocedures in the UE in order to estimate the best beam or beams to beused for data transmission.

One solution to this problem is to transmit BRSs only in a few beams inthe GoB. If the directions to all active UE:s are known, the UE:s arenot moving, and no new UE:s enter the system, this could be a viableapproach. However, problems will occur if new UE:s enter the systemand/or established propagation paths suddenly are obstructed due to,e.g., a UE moving behind a building. In such cases, the direction to thenew UE or the new dominating propagation path cannot be estimated bymeans of BRSs if no BRSs are transmitted in those directions. This maylead to that active transmissions beams are lost and that new activetransmission beams cannot be established for new UE:s.

There is thus a need for a wireless communication node that is arrangedto handle abrupt changes in dominating propagation paths for existingUE:s and the appearance of new UE:s in a more efficient and reliablemanner than previously known.

SUMMARY

It is an object of the present disclosure to provide a wirelesscommunication node comprising an antenna arrangement and a method forantenna radiation beam control addressing one or more of the aspectsstated above.

Said object is obtained by means of a wireless communication nodecomprising an antenna arrangement that is adapted to radiate at leastone radiation beam of a first type and at least one radiation beam of asecond type. Said at least one radiation beam of the first type has afirst type beamwidth and said at least one radiation beam of the secondtype has a second type beamwidth that exceeds the first type beamwidth.Said at least one radiation beam of the first type is arranged forcommunication with at least a first other node, and said at least oneradiation beam of the second type is arranged for detection of changesin propagation paths for said other node and/or appearances of furtherother nodes.

Said object is also obtained by means of a method for antenna radiationbeam control, comprising radiating at least one radiation beam of afirst type and radiating at least one radiation beam of a second type;wherein said at least one radiation beam of the first type has a firsttype beamwidth and said at least one radiation beam of the second typehas a second type beamwidth that exceeds the first type beamwidth.

The method further comprises: using said at least one radiation beam ofthe first type for communication with at least a first other node andusing said at least one radiation beam of the second type for detectionof changes in propagation paths and/or appearances of further nodes.

A number of advantages are obtained by means of the present disclosure.Mainly, beam finding and tracking is enabled in a dynamic environmentwith abrupt changes in dominating propagation paths for existing nodes,such as UE:s, and appearance of new nodes, such as UE:s, using a reducedamount of pilots compared to previously known solutions.

According to an example, the antenna arrangement is adapted to change aradiation beam of the second type when an appearance of any other nodehas been detected by said radiation beam. This change comprises formingat least one radiation beam of the first type that is arranged forcommunication with said any other node.

According to another example, the change also comprises maintaining aradiation beam of the second type.

In this manner, the desired functionality is maintained.

According to another example, the change also comprises forming at leasttwo radiation beams of the second type.

According to another example, two or more radiation beams of the firsttype are arranged for communication with each other node in order toenable beam-switching, and/or multi-layer or diversitytransmission/reception.

According to another example, the node is arranged to activate aradiation beam of the second type for a region that has been deprived ofradiation beams of the first type.

In this manner, the desired functionality is provided in an area whereit is needed.

According to another example, the antenna arrangement comprises at leastone antenna array of dual polarized antenna elements that are arrangedfor dual polarization beam-forming.

Generation of a GoB with beams having adjustable beamwidths with full PAutilization is enabled in the case of an active antenna arrayarchitecture based on dual polarization beam-forming (DPBF).

More examples are disclosed in the dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure will now be described more in detail withreference to the appended drawings, where:

FIG. 1 shows a side view of a wireless communication node;

FIG. 2 shows a schematic view of a wireless communication node thatcommunicates with UE:s where a new UE appears;

FIG. 3 shows an alternative step for radiation beam change;

FIG. 4 shows a completed radiation beam change;

FIG. 5 shows an alternative for radiation beam generation;

FIG. 6 shows an alternative for radiation beam generation when a UE hasleft;

FIG. 7 shows another alternative for radiation beam generation;

FIG. 8 shows a schematic view of a wireless communication node thatcommunicates with a UE;

FIG. 9 shows a schematic view of detection of a new propagation pathwhen the UE in FIG. 8 is obscured;

FIG. 10 shows a schematic view of a generated new propagation path;

FIG. 11 shows a schematic view of an antenna array of dual polarizedantenna elements;

FIG. 12 shows a flowchart for a method according to the presentdisclosure; and

FIG. 13 illustrates a wireless communication node arrangement accordingto some aspects of the present disclosure.

DETAILED DESCRIPTION

With reference to FIG. 1 and FIG. 2, there is a wireless communicationnode 1 comprising an antenna arrangement 2 that is adapted to radiatesix radiation beams 3, 4, 5; 6, 7, 8 of a first type and one radiationbeam 9 of a second type. A first set of three radiation beams 3, 4, 5are arranged for communication with a first user terminal, userequipment (UE) 10, and a second set of three radiation beams 6, 7, 8 arearranged for communication with a second UE 11.

According to the present disclosure, the radiation beams 3, 4, 5; 6, 7,8 of the first type has a first type beamwidth BT1 and each one of theradiation beam 9 of the second type has a second type beamwidth BT2 thatexceeds the first type beamwidth BT1. The radiation beams 3, 4, 5; 6, 7,8 of the first type are relatively narrow and arranged for communicationwith the UE:s 10, 11, constituting active radiation beams. A reason forhaving more than one active beam per UE is to enable beam switching whenthe UE moves. They can also be used for multi-layer or diversitytransmission/reception if the channel conditions are suitable for that.Note that all active beams need not transmit or receive data. An activeUE 10, 11 measures RSRP for these beams 3, 4, 5; 6, 7, 8 in order toenable a beam switch if another beam becomes more favorable.

The radiation beam 9 of the second type is constituted by a monitoringbeam that has a relatively wide beamwidth and is arranged for detectionof changes in propagation paths for the UE:s 10, 11 and/or appearancesof further other UE:s, in FIG. 2 indicated by the appearance of a thirdUE 12. As indicated in FIG. 2, there are thus three narrow beams 3, 4,5; 6, 7, 8 per UE 10, 11 that illustrate the active beams where beamreference signals (BRS:s) are transmitted. These can be used to tracksmall movements of the UE:s 10, 11 which could lead to a change of bestserving beam.

When the third UE 12 that requests establishment of data communicationit is detected by the radiation beam 9 of the second type, constitutinga monitoring beam, since there are now other beams in this area. Thethird UE 12 can now detect the BRS in the monitoring beam 9 and reportreference signal received power (RSRP) to the communication node 1.

According to some aspects, the antenna arrangement 2 is adapted tochange the radiation beam 9 of the second type. In this example, asshown in FIG. 4, the change comprises forming three radiation beams 16,17, 18 of the first type that are arranged for communication with thethird UE 12. These radiation beams 16, 17, 18 of the first type are usedfor subsequent data transmission and beam tracking.

This change is according to some aspects performed in steps, as shownalso with reference to FIG. 3. Here, the change first comprises forminga plurality of radiation beams 13, 14, 15 having a first beamwidth B1 inorder to obtain first direction information for the third UE 12, andthen forming the three radiation beams 16, 17, 18 of the first typehaving a second beamwidth B2 as shown in FIG. 2 in order to obtainsecond direction information for the third UE 12. The first beamwidth B1falls below the beamwidth BT2 of the radiation beam 9 of the secondtype, and the second beamwidth B2 falls below the first beamwidth B1.The accuracy of the second direction information exceeds the accuracy ofthe first direction information.

To maintain full coverage of BRS:s, two different examples for havingadditional wide monitoring beams will be described.

As shown in FIG. 5 and FIG. 6, two radiation beams 20, 21; 22, 23 of thesecond type, i.e. two monitoring beams that do not overlap with theactive beams, are formed. The two monitoring beams that 20, 21 in FIG. 5are not as wide as the two monitoring beams that 22, 23 in FIG. 6.

As shown in FIG. 7, only one wide beam 19 of the second type is usedinstead.

In the following a further example will be presented with reference tothe FIGS. 8-10.

With reference to FIG. 8, there is an established data communicationbetween the communication node 1 and a UE 28 using three narrow activebeams 24, 25, 26 of the first type, and there is one wide monitoringbeam 27 of the second type. Furthermore, there are two buildings, afirst building 39 and a second building 40. As shown in FIG. 8, the UE28 is not obstructed by any of the buildings 39, 40, and datatransmission can be performed using the three active beams 24, 25, 26.

As shown in FIG. 9, the UE 28 moves such that the first building 39obstructs the UE 28 from the active beams 24, 25, 26. It is hereapparent that a reflection path 41 via the second building 40 can beutilized for the data transmission. This auxiliary propagation path 41is detected by the UE 28 thanks to the BRS transmitted in the widemonitoring beam 27.

As shown in FIG. 10, data transmission is now performed by using threenew narrow active beams 29, 30, 31 of the first type utilizing thereflection path 41 in building B has been established while the previousactive beams 24, 25, 26 have been released and replaced by a new widemonitoring beam 42 of the second type. Generally, the communication node1 is thus arranged to activate a radiation beam 42 of the second typefor a region that has been deprived of radiation beams of the first type24, 25, 26.

Generating a GoB (Grid of Beams) with beams having adjustable beamwidthsis according to an aspect enabled by means of an antenna arrangement 2of the communication node 1 that is constituted by an active antennaarray architecture based on dual polarization beam-forming (DPBF). Withreference to FIG. 11, the antenna arrangement 2 of the communicationnode 1 comprises at least one active two-dimensional antenna array 32 ofdual polarized antenna elements 33, 34 that are arranged for dualpolarization beam-forming.

According to an aspect, each element and polarization has its own poweramplifier (PA); this architecture enables adjustable beamwidths whilemaintaining full (PA) utilization in the active antenna array 32.

A method and active antenna array architecture is therefore according toan aspect based on DPBF for beam finding and tracking in a massivebeamforming system using GoB. Narrow active beams track UE:s withestablished data communication, while simultaneously having widemonitoring beams to detect changes in dominating propagation paths orthe appearance of new UE:s. The mix of narrow and wide beams in the GoBis achieved with full PA utilization when using a DPBF active antennaarray architecture.

The beam finding and tracking is able to handle abrupt changes indominating propagation paths for existing UE:s and the appearance of newUE:s, and is according to some aspects based on generating a GoB wherethe different beams being of different types that have differentbeamwidths that are adapted to the current situation. The GoB consistsof a simultaneous mix of narrow beams of the first type to cater fordata transmission to active UE:s and wide beams of the second type to beable to discover new UE:s, as in the examples described with referenceto FIG. 2-7, or new propagation paths to already active UE:s, as in theexample described with reference to FIG. 8-10. According to an aspect,the narrow beams and the wide beams together give a complete coverageover an entire sector.

The first type beamwidth BT1 is not intended to be regarded as a certainvalue, but as a beamwidth span since all the radiation beam 3, 4, 5; 6,7, 8 of the first type do not necessarily have to have identicalbeamwidths and beam-shapes, but where these may differ with a certainspan, where this span is defined by the first type beamwidth BT1. Thesame reasoning is valid for the second type beamwidth BT2, the firstbeamwidth B1 and the second beamwidth B2. Most importantly the firsttype beamwidth BT1 is relatively narrow and the second type beamwidthBT2 is relatively wide such that the disclosed beam finding and trackingis enabled as described above.

In this context, according to some aspects and only as an example, arelatively wide beamwidth has a half-power beamwidth that at least istwice as wide as the half-power beamwidth of a relatively narrowbeamwidth

The present disclosure is not limited to the examples above, but mayvary within the scope of the appended claims. For example, it is notnecessary that massive beamforming such as GoB is used; any type ofbeamforming that enables the disclosed beam finding and tracking isconceivable.

The number of radiation beams of the first type and the number ofradiation beams of the second type may vary. Generally, there is atleast one radiation beam of the first type and at least one radiationbeam of the second type.

It is not necessary that the antenna arrangement 2 is adapted to radiatemore than one active beam per UE, but it is also conceivable that theantenna arrangement 2 is adapted to radiate two active beams per UE ormore. As understood from the examples, the antenna arrangement 2 isfurthermore adapted to radiate at least one radiation beam 9 of thesecond type.

It is not necessary that a new radiation beam of the second type isgenerated after a change where an initial radiation beam of the secondtype has been changed to one or more radiation beams of the first type,due to for example new UE:s that are discovered, or new propagationpaths to already active UE:s. According to some aspects, possiblegeneration of new radiation beam of the second type depends on otheralready existing radiation beams of the second type, sector layout,antenna arrangement capacity etc.

The UE:s are generally constituted by any types of suitable nodes suchas for example any type of user terminals.

The antenna array can be one-dimensional as well as two-dimensional.

Generally, the present disclosure relates to a wireless communicationnode 1 comprising an antenna arrangement 2 that is adapted to radiate atleast one radiation beam 3, 4, 5; 6, 7, 8 of a first type and at leastone radiation beam 9 of a second type. Said at least one radiation beam3, 4, 5; 6, 7, 8 of the first type has a first type beamwidth BT1 andsaid at least one radiation beam 9 of the second type has a second typebeamwidth BT2 that exceeds the first type beamwidth BT1, where said atleast one radiation beam 3, 4, 5; 6, 7, 8 of the first type is arrangedfor communication with at least a first other node 10, 11, and wheresaid at least one radiation beam 9 of the second type is arranged fordetection of changes in propagation paths for said other node 10, 11and/or appearances of further other nodes.

According to an example, the antenna arrangement 2 is adapted to changea radiation beam 9 of the second type when an appearance of any othernode 12 has been detected by said radiation beam 9, where the changecomprises forming at least one radiation beam 13, 14, 15 of the firsttype that is arranged for communication with said any other node 12.

According to an example, the change first comprises forming a pluralityof radiation beams 13, 14, 15 having a first beamwidth B1 in order toobtain first direction information for said any other node, and thenforming a plurality of radiation beams 16, 17, 18 having a secondbeamwidth B2 in order to obtain second direction information for saidany other node 12, where the first beamwidth B1 falls below the secondtype beamwidth BT2, where the second beamwidth B2 falls below the firstbeamwidth B1, and where the accuracy of the second direction informationexceeds the accuracy of the first direction information.

According to an example, the radiation beams 16, 17, 18 having a secondbeamwidth B2 are constituted by radiation beams of the first type.

According to an example, the change also comprises maintaining aradiation beam 19 of the second type.

According to an example, the change also comprises forming at least tworadiation beams 20, 21; 22, 23 of the second type.

According to an example, two or more radiation beams 3, 4, 5; 6, 7, 8;16, 17, 18; 24, 25, 26; 29, 30, 31 of the first type are arranged forcommunication with each other node 10, 11, 12; 28 in order to enablebeam-switching, and/or multi-layer or diversity transmission/reception.

According to an example, wherein the node 1 is arranged to activateand/or de-activate one or more radiation beams 6, 7, 8; 16, 17, 18; 24,25, 26; 29, 30, 31 of the first type in dependence of measuredcommunication properties.

According to an example, the node 1 is arranged to activate a radiationbeam 23 of the second type for a region that has been deprived ofradiation beams of the first type 6, 7, 8.

According to an example, the antenna arrangement 2 comprises at leastone antenna array 32 of dual polarized antenna elements 33, 34 that arearranged for dual polarization beam-forming.

Generally, the present disclosure also relates to a method for antennaradiation beam control comprising:

35: radiating at least one radiation beam 3, 4, 5; 6, 7, 8 of a firsttype; and

36: radiating at least one radiation beam 9 of a second type; whereinsaid at least one radiation beam 3, 4, 5; 6, 7, 8 of the first type hasa first type beamwidth BT1 and said at least one radiation beam 9 of thesecond type has a second type beamwidth BT2 that exceeds the first typebeamwidth BT1, where the method further comprises:

37: using said at least one radiation beam 3, 4, 5; 6, 7, 8 of the firsttype for communication with at least a first other node 10; and

38: using said at least one radiation beam 9 of the second type fordetection of changes in propagation paths and/or appearances of furthernodes 11, 12.

According to an example, the method further comprises changing aradiation beam 9 of the second type when an appearance of any other node12 has been detected by said radiation beam 9, where the changecomprises forming at least one radiation beam 13, 14, 15 of the firsttype that is used for communication with said any other node 12.

According to an example, the change first comprises forming a firstplurality of radiation beams 13, 14, 15 having a first beamwidth B1 inorder to obtain first direction information for said any other node, andthen forming a plurality of radiation beams 16, 17, 18 having a secondbeamwidth B2 in order to obtain second direction information for saidany other node 12, where the first beamwidth B1 falls below thebeamwidth BT2 of the radiation beam 4 of the second type, where thesecond beamwidth B2 falls below the first beamwidth B1, and where theaccuracy of the second direction information exceeds the accuracy of thefirst direction information.

According to an example, the radiation beams 16, 17, 18 having a secondbeamwidth B2 are constituted by radiation beams of the first type.

According to an example, the change also comprises maintaining aradiation beam 19 of the second type.

According to an example, the change also comprises forming at least tworadiation beams 20, 21; 22, 23 of the second type.

According to an example, the method comprises using two or moreradiation beams 3, 4, 5; 6, 7, 8; 16, 17, 18; 24, 25, 26; 29, 30, 31 ofthe first type for communication with each other node 10, 11, 12; 28,enabling beam-switching, and/or multi-layer or diversitytransmission/reception.

According to an example, the method comprises activating and/orde-activating one or more radiation beams 6, 7, 8; 16, 17, 18; 24, 25,26; 29, 30, 31 of the first type in dependence of measured communicationproperties.

According to an example, the method comprises activating a radiationbeam 23 of the second type for a region that has been deprived ofradiation beams 6, 7, 8 of the first type.

According to an example, the two types of radiation beams are obtainedby using dual polarized beam-forming for at least one antenna array 32of dual polarized antenna elements 33, 34.

FIG. 13 shows a wireless communication node arrangement for antennaradiation beam control. The wireless communication node arrangementcomprises a first radiating module X35 configured to radiate at leastone radiation beam 3, 4, 5; 6, 7, 8 of a first type; a second radiatingmodule X36 configured to radiate at least one radiation beam 9 of asecond type, where said at least one radiation beam 3, 4, 5; 6, 7, 8 ofthe first type has a first type beamwidth BT1 and said at least oneradiation beam 9 of the second type has a second type beamwidth BT2 thatexceeds the first type beamwidth BT1; a communication module X37configured to use said at least one radiation beam 3, 4, 5; 6, 7, 8 ofthe first type for communication with at least a first other node 10; adetecting module X38 configured to use said at least one radiation beam(9) of the second type for detection of changes in propagation pathsand/or appearances of further nodes (11, 12).

1-20. (canceled)
 21. A network node, the network node comprising an antenna arrangement, wherein the network node is configured to: employ the antenna arrangement to radiate at least a first beam and a second beam, wherein the first beam has a first beamwidth (B1) and the second beam has a second beamwidth (B2) that is wider than the first beamwidth (B1); use the first beam for communication with at least a first user equipment (UE); use the second beam to detect a movement of the first UE that causes a change in a propagation path for the first UE; and after detecting the movement using the second beam, form a third beam for the first UE and use the third beam to communicate with the first UE, wherein the third beam has a third beamwidth (B3) that is narrower than the second beamwidth (B2).
 22. The network node of claim 21, wherein the antenna arrangement comprises at least one antenna array of dual polarized antenna elements that are arranged for dual polarization beam-forming.
 23. The network node of claim 21, wherein the third beam has the first beamwidth (B1).
 24. The network node of claim 21, wherein the network node is configured to use the second beam to detect the movement of the UE by performing an event detection process that includes using the second beam to transmit a reference signal.
 25. The network node of claim 24, wherein the event detection process further comprises determining that the UE has received the reference signal transmitted using the second beam.
 26. The network node of claim 25, wherein, when the network node determines that the UE has received the reference signal, the network node is further configured to: use a plurality of beams to obtain direction information for the UE; and after obtaining the direction information, use the obtained direction information to form the third beam.
 27. The network node of claim 21, wherein the network node is a second UE.
 28. The network node of claim 21, wherein the network node is a base station.
 29. A method performed by a network node comprising an antenna arrangement, the method comprising: employing the antenna arrangement to radiate at least a first beam and a second beam, wherein the first beam has a first beamwidth (B1) and the second beam has a second beamwidth (B2) that is wider than the first beamwidth (B1); using the first beam for communication with at least a first user equipment (UE); using the second beam to detect a movement of the first UE that causes a change in a propagation path for the first UE; and after detecting the movement using the second beam, forming a third beam for the first UE and use the third beam to communicate with the first UE, wherein the third beam has a third beamwidth (B3) that is narrower than the second beamwidth (B2).
 30. A computer program product comprising a non-transitory computer readable medium storing a computer program comprising instructions for configuring a network node comprising an antenna arrangement to perform the method of claim
 29. 31. A network node, the network node comprising an antenna arrangement, wherein the network node is configured to: employ the antenna arrangement to radiate at least a first beam and a second beam, wherein the first beam has a first beamwidth (B1) and the second beam has a second beamwidth (B2) that is wider than the first beamwidth (B1); use the first beam for communication with at least a first user equipment (UE); use the second beam to detect an appearance of a second UE; and after detecting the appearance of the second UE using the second beam, form a third beam for the second UE and use the third beam to communicate with the second UE, wherein the third beam has a third beamwidth (B3) that is narrower than the second beamwidth (B2).
 32. The network node of claim 31, wherein the network node is further configured to form and use the third beam to communicate with the second UE after detecting the appearance of the second UE using the second beam.
 33. The network node of claim 32, wherein the network node is further configured such that, prior to forming the third beam, the network node forms a first plurality of beams having a fourth beamwidth (B4) and uses the first plurality of beams to obtain first direction information for the second UE.
 34. The network node of claim 33, wherein the network node is further configured to: form a second plurality of beams having the third beamwidth (B3), and use the second plurality of beams to obtain second direction information for the second UE, wherein the fourth beamwidth (B4) is narrower than the second beamwidth (B2), the third beamwidth (B3) is narrower than the fourth beamwidth (B4), and the accuracy of the second direction information exceeds the accuracy of the first direction information.
 35. The network node of claim 31, wherein the antenna arrangement comprises at least one antenna array of dual polarized antenna elements that are arranged for dual polarization beam-forming.
 36. The network node of claim 31, wherein the third beam has the first beamwidth (B1).
 37. The network node of claim 31, wherein the network node is configured to use the second beam to detect the appearance of the second UE by performing an event detection process that includes using the second beam to transmit a reference signal.
 38. The network node of claim 37, wherein the event detection process further comprises determining that the second UE has received the reference signal transmitted using the second beam.
 39. The network node of claim 38, wherein, when the network node determines that the second UE has received the reference signal, the network node is further configured to: use a plurality of beams to obtain direction information for the second UE; and after obtaining the direction information, use the obtained direction information to form the third beam.
 40. The network node of claim 31, wherein the network node is a third UE.
 41. The network node of claim 31, wherein the network node is a base station.
 42. A method performed by a network node comprising an antenna arrangement, the method comprising: employing the antenna arrangement to radiate at least a first beam and a second beam, wherein the first beam has a first beamwidth (B1) and the second beam has a second beamwidth (B2) that is wider than the first beamwidth (B1); using the first beam for communication with at least a first user equipment (UE); using the second beam to detect an appearance of a second UE; and after detecting the appearance of the second UE using the second beam, forming a third beam for the second UE and use the third beam to communicate with the second UE, wherein the third beam has a third beamwidth (B3) that is narrower than the second beamwidth (B2).
 43. A computer program product comprising a non-transitory computer readable medium storing a computer program comprising instructions for configuring a network node comprising an antenna arrangement to perform the method of claim
 42. 